I have a 2000 Blazer with the push button auto and hi, low.One day my 2wd hi light started flashing and would not go into 4wd.I tried to reset it by disconnecting the battery and reconnecting it.After that all the lights went out on the push buttons and still no 4wd.I took it to a transmission shop and they replaced the ATC fuse and said it was my TCCM.I got a new one and that didn't fix anything.So I reconnected my old one and drove it.When I restarted my engine one day all the lights on the switch were flashing and the TCCM was clicking like crazy, after a few minutes my 2wd hi light came on and the 4wd hi and low worked.Two days later everything stopped working.I read here on the forums about corroded contacts so I tried cleaning them with automotive contact cleaner.Now some days I get the 2wd light and try to go into 4wd and it just flashes with no clicking coming from the TCCM. On other days I get the service 4wd light and nothing else.If anyone can help with this I would appreciate it.